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Experimental Evidence for s-Wave Pairing Symmetry in Superconducting Cu_{x}Bi_{2}Se_{3} Single Crystals Using a Scanning Tunneling Microscope

Published

Author(s)

Niv Levy, Tong Zhang, Jeonghoon Ha, Fred Sharifi, Alec Talin, Young Kuk, Joseph A. Stroscio

Abstract

Topological superconductors (TS) are a newly predicted phase of matter which is topologically distinct from conventional superconducting condensates of Cooper pairs. As a manifestation of its topological character, TS supports massless itinerant quasi-particles on the boundary, which are solid-state realizations of Majorana fermions. The recently discovered superconductor CuxBi2Se3 has been theoretically proposed as an odd-parity superconductor in the time-reversal-invariant TS class. Here we report scanning tunneling spectroscopy (STS) measurements of the superconducting energy gap in CuxBi2Se3 as a function of spatial position and applied magnetic field. The tunneling spectrum shows that the density of states at the Fermi level is fully gapped without any in-gap states. The spectrum is well described by the Bardeen-Cooper-Schrieffer (BCS) theory with a momentum independent order parameter, which strongly suggests that Cu0.2Bi2Se3 is a classical s-wave superconductor contrary to previous expectations.
Citation
Physical Review Letters
Volume
110
Issue
11

Keywords

Topological superconductors, scanning tunneling microscopy, scanning tunneling spectroscopy
Created March 12, 2013, Updated February 19, 2017